Overcharged given credits and they've never been applied.

I have been getting random overcharges for the last couple years. Overages due to data use. But they do not make any sense when I am told one day that I am at 75% of my limit, the next day 90%, and the next over on my account. I have been charged for overages when we had actually had adults move from the residence, a child that used a tablet all day that started school, and switched all devices and streaming apps to the lowest rate possible. Yet still random months of extreme overages. I was charged an additional $120 on top of my normal $45 bill.  I have been given credits that you can see on my account but they never apply them and have the audacity to charge me change my plan then not even prorate it correctly. In just a matter of a few months this year they charged me over $230 in additional charges that make ZERO sense. Every time I call they acknowledge the credits and have to push it higher up, offer additional credits, etc. I do not get any resolution to the credits I already have not being applied. I have not received the credits I was told would be used to adjust for the obscene and random overages. The tickets that were opened were closed with no resolution. The supervisor that was supposed to call me did not until days later. I am on hold for hours just to have the call dropped. If anyone is reading this, go with ATT... they suck too, but not this bad.